The only way you could have locked notes in the first place is to set up a password, only then you can you allow Touch ID to unlock the notes. So you did set up a password at some point.
Touch ID is a convenience and it does not replace your password, therefore you cannot forget it.
It's not really any different than using Touch ID to unlock your phone. There are things that can & will occur that require re-entry of the password/passcode. If you forget your iPhone passcode and rely on Touch ID, you'll wind up in the same position with your phone.
If you don't recall the notes password, you will not be able to access your locked notes.
You can use the link below to reset your password for notes that you lock going forward.
How to lock notes on your iPhone, iPad, and iPod touch - Apple Support